Anything that follows a predictable and repeated pattern but eventually ends back right where it started. Most useful for degenerate or addictive people who try (generally half-hearted) to change ingrained behavior.

Got drunk and called my ex for a booty-call last night. We're already fighting again - why am I cursed by this cycular shit?
My buddy Ian is quitting smoking AGAIN. What a cycular waste of time...
Went to a frat party last week and woke up in a pile of my own vomit with the word "penis" in indelible ink on my forehead. Totally cycular behavior but its mostly worn off, and they are having another party tonight!